Fan or blower



Oct. 18, 1932. N. F. T.. SAUNI'SERS FAN OR BLOWER Filed Nov. 1, 1929 3Sheets-Sheet l r: wan/j INVENTOR Norman E. I Saunders Oct. 18, 1932.

N. F. T. SAUNDERS FAN 0R BLOWER 3 Sheets-Sheet 2 Filed Nov. 1. 1929 INVE NTOR Norman E 7T; Saunders ATTORNEY I Oct. 18, 1932. N. F. T. SAUNDERSFAN OR BLOWER Filed Nov. 1. 1929 5 Sheets-Sheet 5 INVENTOR Norman. ff TSaunders ATTORNEY Patented Oct. 18, 1932 UNITED STATES PATENT OFFICENORMAN FRANK TILIBURY SAUNDERS, OF NEWPORT PAGNELL, ENGLAND, ASSIGNOR TOASSOCIATED ELECTRICAL INDUSTRIES LIMITED, A COMPANY OF GREAT BRITAIN FANOR BLOWER Application filed November 1, 1929, Serial 110.403,.972, andin Great Britain November 2, 1928.

The invention relates to fans or blowers, its object being to provideimproved constructions or arrangements of the blading thereof which willbe particularly advantageous in cases where the fan or blower may berequired to operate in both directions of rotation, as for example inthe case of the ventilation fans for reversible types of dynamo electricmachines.

For such machines it is usual to employ fans or impellers comprising anumber of blades disposed more or less radially between a pair ofshrouds,'one of which may be in the form of a disc secured to the rotorshaft while the other may take the form of an annulus or spider. The airis drawn in through the centre or eye of the annular shroud and impelledoutwardly by the blades. If the blades are truly radial, the etliciencyof the impeller will be the same for both directions of rotation,whereas by curving the blades a higher efliciency may be obtained forone direction of rotation, but not for the other direction.

According to the present invention a fan or blower is provided withblades the inlet and/or leaving edges of which are disposed at an angleto the radial direction, the mounting of the blades in the impellerbeing such that said angle can be reversed from one side to the other ofthe radial direction. The blades are preferably mounted upon the shroudsso as to be capable of pivoting, when permitted to do so, about axessubstantially parallel to the axis of the impeller and substantiallyequidistant from the ends of the appurtenant blades, the latter eachbeing curved to a form which is symmetrical about an axis normal to thecentre of the blade surface and passing through the pivotal axisaforesaid. The reversal of the blades when desired is thus effected by apivotal movement.

The blades may be movable individually or as a whole, while pivotalmovement thereof may be effected by hand or automatically upon reversalof the direction of rotation of the impeller. Automatic movement of theblades into the position appropriate to the direction of rotation may beadapted to be upon rotation of the impeller and in some cases camdevices may be provided to effect or to assist in the movement of theblades, when necessary, into the appropriate position.

The inclination of the blades-for each direction of rotation may have apredetermined preferred Value or may be adjustable, and according to afurther feature of theinvention the blades may be weighted and pivotedin such a manner that the inclination of the blades may be varied bycentrifugal action according to the speed of rotation of the impeller.

In order that the invention may be clearly understood and readilycarried into effect a number of constructions according thereto arehereinafter described with reference to the accompanying drawings,wherein-' Figs. 1, 2 and 3 are respectively a sectional elevation, crosssection and plan showing a portion of an impeller and blade arrangedaccording to one constructional form of the invention. 7

Figs. 4 and 5 are respectively a sectional elevation and plan showing amodified construction. I

Figs. 6 and 7 are respectively a sectional elevation and cross sectionshowing a construction in which the blades are automatically reversibleupon reversal of the direction of rotation of the impeller. 1

Fig. 8 is a diagrammatic view illustrating certain of the blades of animpeller such as shown in Fig. 6, in the positions which they occupywhen the impeller is at rest, and

Fig. 9 is a sectional elevation on line XIIIXIII of Fig. 10, and Fig. 10isa cross section on line XIV-XIV of Fig. 9,.shoW- ing a furthermodified construction according to the invention.

Similar parts are indicated by similar reference numerals in all thefigures.

The blades 1 in the examples illustrated are of a curved form,advantageously pressed from sheet metal with lugs 2at each side fromwhich bearing sleeve portions 3 are extruded. The blades are pivotallymounted in the shroud rings 4, 5 of the impeller in any suitable manner,for example as indicated in Fig. 2, or with the addition of studs 6 asindicated in Fig. 7.

In all cases the curved form of the blade is symmetrical about an axissuch as l I (Fig. 1) normal to the centre of the blade surface andpassing through the axis about Which the blade is rotatable, which axisit will be observed is parallel to the axis of rotation of the impeller.In the examples shown the outer or leaving edge 8 of the blade isdisposed substantially radially of the impeller when in the normal oroperative position, while the inner or inlet edge 9 forms a substantialangle with the radial direction. The forms or angles of the inlet andleaving edges of the blades may obviously be otherwise shaped andarranger as may be preferred according to the well known principles ofdesign as applied to the conditions under which the impeller is requiredto operate. In the construction shown in Figs. 1, 2 and 3, the blade 1is held in operative position by means of a U-shaped member 10 securedto the shroud l by a nut 11 and bolt 12, one limb of the U-memberforming an abutment for the back or convex side of the blade near theleaving edge, while the other limb coacts with the side of the nut 11 tolock same. The inner or inlet edge portion 9 of the blade 1 rests withits back or convex side against an abutment pin 13 secured to the shroud4c, and is pressed firmly against said pin when the bolt 12 istightened.

The blade when in the position shown in Fig. 1 is adapted for clockwiserotation of the impeller. If it is desired to rotate the impeller in theopposite direction the blade should be reversed into the positionindicated by dotted lines. This may be accomplished by slackening thebolt 12to permit the U- member 10 to be removed, whereupon the blade 1may be rotated until the portion 8 which previously constituted theleaving edge rests with its back against second abutment pin 13 TheU-member 10 may then be reapplied so that one limb engages the convexside of the outer portion of the blade in its new position. It will beobserved that in this arrangement the centre of the bolt 12 is in aposition to be intersected by a radius IIII of the impeller passingthrough the pivotal axis of the blade, while the pins 13, 13 are equallysoaced on either side of. such radius.

Figs. l and 5 show a construction substan tially similar to that shownin Fig. 1, but in which tongues, 14, 14 pressed out of the material ofthe shroud l are provided instead or" the U-member 10 of Fig. 1. lnorder to reverse the blade from the position shown in Fig. 4, it is onlynecessary to depress the tongue 1d and to rotate the blade in theanticlockwise direction unt-il it is engaged by the tongue l l asindicated by dotted lines in Fig. 5. The tongues 14, 1& are preferablyresilient.

With constructions such as described above with reference to Figs. 1-5it is necessary to reverse each blade individually by hand. Such anarrangement has the advantage of simplicity of construction and wouldgenerally be used in cases where the impeller is required to operatewith a constant direction of rotation, which direction is howeverunknown at the time the impeller is constructed. In cases where theimpeller may be required to undergo frequent changes of directionhowever, it is preferred to employ a construction whereby all the bladesmay be automatically reversed or simultaneously re versed by a simpleoperation.

Constructions may be provided ccording to the invention whereby theblades may be automatically reversed upon reversal of the dire tion ofrotation of the impeller. The inertia of the blades or of suitableweights connected thereto may be utilized for this purpose, and in someca es cam devices may be )rovided to assist in the reversal. The bladesmay be held in position by centrifugal act on when the impeller is inoperation.

a gs. 38 show an arrangement in which each he has connected to it aweight 16. The weight is carried by a pin 17 which passes through a slot18 in the shroud l, and is spaced at a suitable radius from the pivot 6.Abutment pins 19, 20 on the shroud coact with the bent-up sides 2 or theblade 1 to lin it the inclination of the blade. It will be evident thatupon rotation of the impeller in either direction, the weight 16 and themass of the blade vill tend to take up a position on the side of thepivot 6 'ay from the direction or rotation, and the centrifugal forceor" the weight 16 when the impeller is speeded up will tend to turn theblade still further about its pivot and thus urge the blade into contactwith the limiting abutment pin 19 or 20 as the case may be. Forclockwise rotation of the impeller, the parts will occupy positions asshown in 6.

If desired a cam device may be provided to effect positive reversal ofthe bla le, for example a ring member such as indicated at 21 (Figs. 68)may be secured to a stationary portion of the impeller casing, said ringbeing flattened somewhat at the top as shown at 22 in Figs. 6 and 8. Theweights 16 are 1 u "Hi preferably iotzu oie about thei pinsll anc. thearrangement is such that if the impeller is rotated very slowly so thatcentrifugal and inertia forces are negligible, the blades will be causedby gravity to fall into positions such as indicated in Fig. 8 as theycome to the top of the impeller, the direction of rotation being assumedto be in the clock.- wise direction. The weights will roll on the camrail 21 as they approach and recede from the uppermost position, butwill hang freely suspended when opposite to the flattened portion 22.Thus, as a blade passes from the. uppermost position either to one sideor the other according to the direction of rotation, it will bepositively turned as its weight 16 comes into contact with the surfaceof the cam 21, the weight being moved rearwardly with respect to thedirection of rotation. Each blade will be similarly moved in theappropriate direction during a complete rotation of the i'mpeller, andwill be further turned into the required operative position bycentrifugal action as the speed of the impeller increases.

If the blades are themselves sufliciently heavy, the roller weights 16may be dispensed with, a projection on the blade serving instead toefiect the reversal by making contact with a guide or the like duringstart ing periods.

It is not necessary that the weights employed to ensure the desiredpositioning of the blades be secured directly to the blades. Figs. 9 and10 show by way of example a construction in which a weight 28 is carriedby an arm 24 pivotally mounted externally on the shroud 4 upon thesleeve portion 3 of the blade 1 which passes through and is journalledin the shroud. The sleeve portion 3 is formed with a flange 25, thelower part of which is cut away, while the upper part is shaped toprovide stops adapted to coact with upstanding portions 26 of the arm 24so as to limit the angular movement of the arm relatively to theblade 1. The action of the device is substantially similar to that ofthe weighted blades previously described above, the arrangement beinghowever preferably such that when the blade is forced by the weight intocontact with the stops on the shroud in the limiting position of theblade, the arm and weight are disposed substantially at right angles toa radius of the impeller passing through the pivotal axis of the blade.In this way the effect of the centrifugal force upon the weight may beutilized to a maximum. Vith such a construction it is also not necessaryto form slots in the shrouds such as may reduce the efficiency of theimpeller.

Constructions such as above described with reference to Figs. 610 may beemployed for the purpose of providing an impeller wherein the bladestake up various different angular positions at ditlerent speeds of theimpeller and thereby cause considerable variation in the quantity orvelocity ofthe air orotherfluid passing through the impeller. That is tosay the impeller may be adapted to deliver different predeterminedquantities of air or the like at different speeds, which quantities mayvary to a greater extent than would be possible merely by varying thespeed in a similar manner when using blades of fixed angular position.For this purpose it is only necessary to select a suitable weight forthe pivoted blade and to dispose same so that a balance is effectedbetween the centrifugal force upon the blade and the force exertedthereon by the air passing through the impeller at the various inclinedpositions of the blades and the corresponding speeds of rotatlon.

From the foregoing it will be appreciated that the invention provides afan or blower which may be operated with good efiiciency for eitherdirection of rotation, and that the invention may be carried out in avariety of constructionswhich may be subject to various modifications inaddition to those more spe-' attached to each of said blower elementsand a cam member cooperating with said weight members for reversing theblower elements upon reversal of the direction of rotation of the fan.

In testimony whereof I have hereunto subscribed my name this l lth dayof October, 1929.

NORMAN FRANK TILBURY SAUNDERS.

